CMAKE警告：ROS 2中未使用手动指定的变量

Question

这个问题可能是ROS 2的特定于ROS 2。我定义了一个自定义标志，例如 Hello_ros 。汇编后，cmake发出以下警告：

$ colcon build --allow-overriding examples_rclcpp_minimal_composition --cmake-args -DHELLO_ROS=OFF
Starting >>> realsense2_camera_msgs
Starting >>> examples_rclcpp_minimal_composition
--- stderr: realsense2_camera_msgs
CMake Warning:
  Manually-specified variables were not used by the project:

    HELLO_ROS


---
Finished <<< realsense2_camera_msgs [4.43s]
Starting >>> realsense2_camera
Starting >>> realsense2_description
--- stderr: realsense2_description
CMake Warning:
  Manually-specified variables were not used by the project:

    HELLO_ROS


---
Finished <<< realsense2_description [0.69s]
Finished <<< examples_rclcpp_minimal_composition [8.01s]
--- stderr: realsense2_camera
CMake Warning:
  Manually-specified variables were not used by the project:

    HELLO_ROS


---
Finished <<< realsense2_camera [15.5s]

Summary: 4 packages finished [20.1s]
  3 packages had stderr output: realsense2_camera realsense2_camera_msgs realsense2_description

以下是我工作空间中的软件包：

.
├── minimal_composition
└── realsense-ros

这些软件包取自 minimal_composition 和。如下所示，在publisher_node.cpp:

void PublisherNode::on_timer() {
  auto message = std_msgs::msg::String();

#ifdef HELLO_ROS
  message.data = "ON! " + std::to_string(count_++);
#else
  message.data = "OFF! " + std::to_string(count_++);
#endif

  RCLCPP_INFO(this->get_logger(), "Publisher: '%s'", message.data.c_str());
  publisher_->publish(message);
}

Similarly, cmakelists.txt 被修改如下所示：

add_library(composition_nodes SHARED
            src/publisher_node.cpp
            src/subscriber_node.cpp)

option(HELLO_ROS "Use HELLO_ROS" OFF) # OFF by default

if( HELLO_ROS ) 
target_compile_definitions(composition_nodes
  PRIVATE "MINIMAL_COMPOSITION_DLL"
  PRIVATE HELLO_ROS
)
else()
target_compile_definitions(composition_nodes
  PRIVATE "MINIMAL_COMPOSITION_DLL"
)
endif(HELLO_ROS)

ament_target_dependencies(composition_nodes rclcpp rclcpp_components std_msgs)

问题

如何摆脱此警告？

版本信息

名称	版本
cmake	3.16.3
GCC	9.4.0
Ros	Foxy
Ubuntu	20.04.4 LTS

更新，

因此以下是到目前为止的分析：

1. 我删除了 #else 从 #ifdef hello_ros 并在CPP文件上添加了 #if Hello_ros #else #endif ，如下所示：

     std :: string msg = std :: to_string（count _ ++）;
   
   ＃如果Hello_ros
     msg +=“ hello_ros在！”;
   ＃别的
     msg +=“ hello_ros不关闭！”;
   #endif
   
   #ifdef hello_ros
     msg +=“ hello_ros已定义！”;
   #endif
     message.data = msg;
    

2. 我从 cmakelists.txt 中删除了，以将其转换为以下方式：

     target_compile_definitions（composition_nodes private“ minimal_composition_dll” private“ hello_ros = $ {hello_ros}”）
    

3. 这次我仅选择了我的软件包，然后用 -cmake-args -dhello_ros = on 参数编制了整个工作空间。

观察结果：

• 即使该项目也使用 -dhello_ros = on 编译， #if Hello_ros *** 被编译为＃＃＃否则。
• 不过，我可以看到 #ifdef 已启用。
• 此外，我可以看到 hello_ros 设置为内部cmakelists.txt上，如下所示：

    ./构建/示例_rclcpp_minimal_composition/cmakefiles/composition_nodes.dir/disterinfo.cmake.cmake：15：“ hello_ros = on”
  ./build/examples_rclcpp_minimal_composition/cmakecache.txt:250://use hello_ros
  ./build/examples_rclcpp_minimal_composition/cmakecache.txt:251:hello_ros:bool：bool = on